Steam Heat and Heating Q&A

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Dear NH,

I've been searching the web and couldn't find much on the topic of
steam heat radiators. I live in New jersey and just bought a house
that is over 60 years old. All the radiators are working but one. The
unit in questions was converted several years ago to a baseboard steam
radiator. There is no warmth in the unit at all. Family advice was to
"bleed the unit". I have never lived in a house with
radiators before so I am completely unfamiliar with the process of
"bleeding". Also I can't seem to locate a "bleed"
bolt. any idea?

MY from South Plainfield, NJ

I haven't even seen a steam radiator since my first home, a hundred
year-old two-bedroom shack I bought in
1973. I fondly remember the banging and clanging of the rapidly
expanding iron pipes as the boiler did its work. On my first night there, I slept on the sofa. I didn't have a bed yet! When the
heat went on, I thought the place was haunted!

Steam radiators do not need to be "bled". Bleeding is
done in hot water systems to allow trapped air to escape. There is no
air trapped in steam radiators... it is blown out by the steam!

Steam radiators have a valve that allows steam to escape at a
controlled
rate so that the radiator can heat up. If this valve is clogged with
mineral deposits or stuck shut, no steam can enter the radiator, so it
doesn't heat up! These valves can be unclogged sometimes, but you
would be better off getting a replacement. You should be able to find
the valve under the end cover of the radiator. Most plumbing
supply houses sell generic replacements.

Another possible problem is that the house has settled causing the
pipe leading to the radiator to no longer slope downward towards the
boiler. If this has occurred, the condensation within the radiator
that would normally flow back to the boiler is instead pooling in the
pipe. This can block the movement of steam to the radiator, or cause a
very noisy hammering as pressurized steam bursts through this water
"dam".

The easy solution is to raise the radiator,
if possible on wood
blocks to restore the downward slope. The more difficult
solution, and sometimes the only option, is to do some major league
plumbing OR think about an alternative heating system such as
electrical or propane.

Dear NH,

Could you give a small explanation of steam heat ? My girlfriend heats her
home with a steam furnace. She has a 7 room house, and what we are
wondering about is the noise that comes from the valves on the radiators.
Not all 7 rooms give off this annoying hissing sound when the furnace is
running, right now 3 of the rooms hiss like crazy .. We have changed the
valves, that seems to work for a while and then either the same room or
another room will start the hissing sounds ... Is this hissing sound a
normal function ? And if it is, then why don't all the radiators give off
that noise ?

EW

EW,

Residential steam heating systems typically incorporate a single pipe that
leads from the boiler to each radiator. When the water boils, the steam
rises into the radiators to heat them. When the steam reaches the cooler
radiators, it condenses to water and drains down the pipes back to the
boiler, where it is reheated.

The pressure release valves are designed to keep the steam moving throughout
the system. The "hissing" is a normal function and, generally
speaking, the
more steam that is released, the quicker the radiator heats up. Since the
escaping steam adds moisture to the air in the cooler months, it should be
accepted as a positive, not negative, quality of steam systems... even
though having lived with a steam system for ten years I sympathize that the
noise at times can be irritating!

You didn't mention whether all the radiators had pressure release valves.
If the non-hissing radiators don't have them, that would explain the lack of
hissing. If they do, the valves may be malfunctioning. Generally speaking,
the adjustment and/or size of the pressure valves affects how much hissing
each radiator produces. Radiators on upper floors and radiators that are
further from the boiler are adjusted to release more steam to compensate for
the increased condensation due to the distance from the boiler. Since these
distant radiators take longer to heat up, they also take longer to begin
hissing.

If you haven't, you should have a plumber or HVAC service person check over
the furnace to be sure everything is working as it should. Sometimes minor
adjustments can have a major impact of the efficiency of the system AND your
comfort level.

However, as mentioned earlier, a certain amount of hissing is normal and
does not in and of itself indicate any problems... except annoyance.